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A module that is everything required to understands Druid Segments
/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.druid.query;
import org.apache.druid.guice.annotations.ExtensionPoint;
import org.apache.druid.segment.Segment;
import java.util.concurrent.ExecutorService;
/**
* An interface that defines the nitty gritty implementation details of a Query on a Segment
*/
@ExtensionPoint
public interface QueryRunnerFactory>
{
/**
* Given a specific segment, this method will create a {@link QueryRunner}.
*
* The {@link QueryRunner}, when asked, will generate a {@link org.apache.druid.java.util.common.guava.Sequence} of
* results based on the given segment. This is the meat of the {@link Query} processing and is where the results are
* actually generated. Everything else is just merging and reduction logic.
*
* @param segment The segment to process
* @return A {@link QueryRunner} that, when asked, will generate a
* {@link org.apache.druid.java.util.common.guava.Sequence} of results based on the given segment
*/
QueryRunner createRunner(Segment segment);
/**
* @deprecated Use {@link #mergeRunners(QueryProcessingPool, Iterable)} instead.
* Runners generated with createRunner() and combined into an Iterable in (time,shardId) order are passed
* along to this method with an {@link ExecutorService}. The method should then return a {@link QueryRunner} that,
* when asked, will use the {@link ExecutorService} to run the base QueryRunners in some fashion.
*
* The vast majority of the time, this should be implemented with {@link ChainedExecutionQueryRunner}:
*
* return new ChainedExecutionQueryRunner<>(queryExecutor, toolChest.getOrdering(), queryWatcher, queryRunners);
*
* Which will allow for parallel execution up to the maximum number of processing threads allowed.
*
* @param queryExecutor {@link ExecutorService} to be used for parallel processing
* @param queryRunners Individual {@link QueryRunner} objects that produce some results
* @return a {@link QueryRunner} that, when asked, will use the {@link ExecutorService} to run the base
* {@link QueryRunner} collection.
*/
@Deprecated
default QueryRunner mergeRunners(ExecutorService queryExecutor, Iterable> queryRunners)
{
return mergeRunners(new ForwardingQueryProcessingPool(queryExecutor), queryRunners);
}
/**
* Runners generated with createRunner() and combined into an Iterable in (time,shardId) order are passed
* along to this method with an {@link QueryProcessingPool}. The method should then return a {@link QueryRunner} that,
* when asked, will use the {@link QueryProcessingPool} to run the base QueryRunners in some fashion.
*
* The vast majority of the time, this should be implemented with {@link ChainedExecutionQueryRunner}:
*
* return new ChainedExecutionQueryRunner<>(queryProcessingPool, toolChest.getOrdering(), queryWatcher, queryRunners);
*
* Which will allow for parallel execution up to the maximum number of processing threads allowed.
*
* Unlike {@link #mergeRunners(ExecutorService, Iterable)}, this method takes a {@link QueryProcessingPool} instead
* which allows custom implementations for prioritize query execution on segments.
*
* @param queryProcessingPool {@link QueryProcessingPool} to be used for parallel processing
* @param queryRunners Individual {@link QueryRunner} objects that produce some results
* @return a {@link QueryRunner} that, when asked, will use the {@link ExecutorService} to run the base
* {@link QueryRunner} collection.
*/
QueryRunner mergeRunners(
QueryProcessingPool queryProcessingPool,
Iterable> queryRunners
);
/**
* Provides access to the {@link QueryToolChest} for this specific {@link Query} type.
*
* @return an instance of the toolchest for this specific query type.
*/
QueryToolChest getToolchest();
}